Patent GB-1165922-A (GB)
Title: Braking Systems
IPC: B60T13/66
Filed: 1966-10-20
Abstract: 1,165,922. Electro-pneumatic braking systems. WESTINGHOUSE AIR BRAKE CO. 20 Oct., 1966 [23 Oct., 1965], No. 47067/66. Heading F2F. In a vehicle braking arrangement having a combined electro-dynamic braking system and a fluid operable braking system, a control device is provided for effecting operation of both of the systems and a blending valve device 15 is provided whereby, in the event of a degree of braking available from the electro-dynamic braking system being insufficient for the degree of braking required by the control device, the fluid-operable braking system is operated, through a balancing beam 65, to effect a degree of braking which compensates for the insufficiency of the electro-dynamic system. In the general arrangement shown in Fig. 1, a variable load combined electro-pneumatic and electro-dynamic brake apparatus for an electric motor-propelled vehicle comprises a brake cylinder 1, a main reservoir 2, a supply reservoir 3, a brake pipe 4, a straight air pipe 5, a feed valve or fluid pressure supply pipe 6, a release magnet valve device 7, an application valve device 8, an emergency valve device 9, a fluid operated self-lapping relay valve device 10, an air spring device 11 interposed between a truck frame 12 and a body 13 of the vehicle for supporting the body of the vehicle, a levelling valve device 14 for maintaining a proper pressure between the air spring device 11, whereby the vehicle body 13 is maintained at a constant height above the railway track irrespective of the load on the body 13 and an electro-dynamicpneumatic interlock or blending valve 15. Brake application.-In operation, when it is desired to effect an application of the brakes, and assuming the vehicle to be empty, a straight air service brake application is initiated by deenergizing a release wire 256 and energizing an application wire 257 such that the release magnet valve device 7 is operated to close communication between the straight air pipe 5 and atmosphere via the pipe 254 and a pipe 258, open to atmosphere, the application magnet valve device 8 being operated to establish communication between the pipes 253 and 254. Fluid under pressure flows from the outlet of a feed valve device 16 connected to the main reservoir 2 to the straight air pipe 5 via pipes 248 and 253, the application valve magnet valve device 8 and a pipe 54. The electro-dynamic brake control circuitry is brought into control as a result of which an electro-dynamic brake compensating magnet 63 forming part of the electrodynamic-pneumatic interlock or blending valve device 15 is energized to a degree proportional to the retardation force being obtained from the electro-dynamic brake. Energization of the magnet coil 198 is effective to cause a plunger 208 of the electro-dynamic brake compensating magnet 63 to exert a downward thrust on the left-hand end of a balancing beam 65 pivoted to a fixed pivot 181 to bias the beam 65 in a counter-clockwise direction such that the thrust exerted on the balancing beam is in accordance with the amount of current flowing in the electro-dynamic braking circuit and is a direct function of the pressure in the straight air pipe 5 until such time as the reducing speed of the vehicle or the diminution of the current in the electro-dynamic braking circuit makes it impossible to provide for the required flow of current through the coil 198 necessary for the plunger 208 and the actuating rod 214 to maintain the balancing beam 65 against an adjusting screw 223 as shown in Fig. 2. Fluid under pressure supplied to the straight air pipe 5 by the application magnet valve device 8 flows into a chamber 102 of a variable low power unit 58 via a pipe 21, a double check valve device 20 and the pipe and passageway 103. As the vehicle is empty the load-sensing portion 57 of the device 15 is kept at the position shown in Fig. 2 so that a variable load regulating valve mechanism 59 is not operated to supply fluid under pressure to the chamber 178 above a diaphragm 160 in the brake demand differential type fluid motor 60. Fluid under pressure supplied from the straight air pipe 5 to the chamber 102 in the variable load power unit 58 flows also to chamber 185 of an in shot valve device 61 to deflect its diaphragm at 183 upwardly against the resistance of springs 190 and 196 to urge a stem 197 upwardly to actuate a brake cylinder regulating valve mechanism 62 similar in construction to the variable load regulating valve mechanism 59. Fluid under pressure then flows from the supply reservoir 3 and a chamber 151 through a port 153 past the unseated supply valve 149 and into a lower chamber 28 of a self-lapping relay valve device 10 to effect the supply of a corresponding pressure to the brake cylinder device 1 to cause a light application of the brakes of the vehicle. As the speed of the vehicle reduces in response to the application of the electro-dynamic brake the current flowing through the main coil 198 is reduced and the force transmitted by. the plunger 208 to the left-hand end of the balancing beam 65 is correspondingly reduced and the differential fluid pressure force, as the result of a straight of the straight air pipe pressure in the chamber 176 between the annular diaphragms 159 and 160 of the brake demand differential type fluid motor 60 is transmitted to the right-hand end of the balancing arm 65 via a stem 173 to rock the balancing beam 65 clockwise about the pivot pin 181. This movement is transmitted to the brake cylinder regulating valve mechanism 162 to effect upward deflection of the annular diaphragm 107 to unseat the supply valve 149 such that fluid under pressure flows from the supply reservoir 3 and the chamber 151 to the lower chamber in the self-lapping relay valve device 10 to effect the supply of a corresponding pressure to the brake cylinder device 1 to cause an increase in the degree of brake application on the vehicle above that effected by operations of the in shot valve device 61 as described above. Thus, as the electro-dynamic brake fades away and the amount of current flowing through the magnet coil 198 of the electrodynamic brake compensating magnet 63 decreases the brake demand differential-type fluid motor 60, in response to the fluid under pressure supplied thereto from the straight air pipe 5, operates the brake cylinder regulating valve mechanism 62 via the balancing beam 65 to increase the pressure in the lower chamber of the self-lapping relay valve device 10 to cause this relay valve device to effect a corresponding increase in brake cylinder pressure supplied to the brake cylinder device 1. Further, as the electro-dynamic brake fades away, the pneumatic brake force is increased to compensate for the fading away of the electro-dynamic brake such that the electro-dynamic brake and the pneumatic brake are blended together, whereby there is no reduction in the total braking effect on the vehicle as the electrodynamic brake fades away. As the body 13 of the vehicle provided with the apparatus as shown in Fig. 1 is loaded, the levelling valve device 14 operates in response to the increase in load to supply fluid under pressure from the feed valve pipe 6 to the chamber 44 of the air spring device 11 via pipes 48 and 45 to establish in the chamber 44 a pressure which is sufficient to maintain the vehicle body 13 at a pre-selected height relative to the truck frame 12 and the rails of the railway track. The chamber 69 in the load-sensing portion 57 of the electrodynamic-pneumatic blending valve device 15 is connected to the pipe 45 via the passageway and pipe 45a and as the pressure in the chamber 44 in the air spring device 11 is increased the pressure in the chamber 69 is increased correspondingly and the diaphragm follower 73 and its stem 74 urge a carriage member 78 to the left from the position shown in Fig. 2 of the drawings so that rollers 84 provided on the carriage member 78 are moved leftwardly with the carriage member 78 in direct proportion to the load on the vehicle, this causes the proportioning lever 118 to be rocked clockwise about a fixed shaft 119 to actuate the variable loadregulating valve mechanism 59 and adjust the braking intensity on the vehicle according to the vehicle load. An emergency valve device 9 is provided which controls the supply of brake pressure from the brake pipe 4 to the pipe 22 leading to a by-pass valve device 18 to the relay valve device 10 and also flows to the pipe and passageway 103 via the double check valve device 20.